Conductive resins have been adopted for the application to antistatic components, plastic electronic components of electronic products, and the like. In particular, these resins are employed in cases where an addition of a metal layer or the like over a resin surface or the like is not enough to achieve sufficient performance. Since an increasing number of electronic components are made of plastics and new applications for electronic components are being explored day by day, the development of conductive resins is important from industrial and commercial points of view.
Polyacetylene and the like can be exemplified as a resin that has a conductive property by itself. However, such a conductive resin often fails to display sufficient performance in practical use. For example, if the lubricity of a fluorine-based resin or the like is necessary, and if at the same time the conductive property is also necessary, the fluorine-based resin or such a non-conductive resin has to be rendered conductive by adding a conductive material such as carbon black.
However, if carbon black is used as such a conductive material, the conductivity of the carbon black itself is low. Thus, a large amount of carbon black has to be added. In cases where the dose of a conductive material is large in this way, a problem arises in that the molding property and the strength of the resin is lowered.
Accordingly, in order to avoid such a problem, it is necessary to reduce the dose of the conductive material as much as possible, and also the conductive material to be added has to be highly conductive. Such a highly conductive material can be exemplified by a carbon nanotube and such a carbon nano-material.
Since these carbon nano-materials contain a large amount of free electrons, they have excellent conductivity. In addition, since carbon nano-materials are hydrophobic, they have a high affinity with resins. Therefore, a carbon nano-material is readily dispersed in a resin as well as being firmly fixed within the resin. Accordingly, carbon nano-materials have excellent properties as an additive to render a resin conductive. However, since these carbon nano-materials are expensive, it is necessary to reduce the dose of the carbon nano-material even lower so as to reduce the price of the conductive resin as a resulting product.
At the present stage, such a carbon nano-material is evenly added in a resin before use. Examples of preceding techniques are disclosed in Japanese Unexamined Patent Application, First Publication No. 2003-100147 (Patent Document 1), Japanese Unexamined Patent Application, First Publication No. 2003-192914 (Patent Document 2), and Japanese Unexamined Patent Application, First Publication No. 2003-221510 (Patent Document 3).
Another example of a conductive material capable of rendering a resin conductive by the addition to the resin can be given by a nanometal. Such a nanometal means superfine particles made of a metal having a diameter or an outer diameter of 1 to 100 nm. Particularly, nanometals made of gold, silver, and such noble metals have excellent conductivity and corrosion resistance. These nanometals are capable of rendering a resin highly conductive with a little amount of dose.
Nanometals per se are not hydrophobic but can be rendered hydrophobic by coating without worsening the conductivity, by which the affinity with a resin can be improved. Such coating can be applied for rendering a nanometal made from copper or such a base metal, to be corrosion resistant. Accordingly, such a nano-base metal can also be adopted as a conductive material to be added to a resin.
However, the cost of the raw material is expensive if a noble metal is adopted as a nanometal, while the cost of coating or such working is expensive if a base metal is adopted. In other words, the cost is expensive in either way. Accordingly, it is necessary to reduce the dose of the nanometal even lower so as to reduce the price of the conductive resin as a resulting product.
At the present stage, such a nanometal is evenly added in a resin before use. Examples of preceding techniques are disclosed in Japanese Unexamined Patent Application, First Publication No. 2003-315531 (Patent Document 4) and Japanese Unexamined Patent Application, First Publication No. 2004-87427 (Patent Document 5).